This invention relates to water saving devices for toilets, and in particular those of the type which float up and down on the overflow tube, where downward movement of the device brings it into contact with the flapper valve at the bottom of the toilet tank in order to close it prematurely, thereby reducing the amount of water used for the flush.
Such devices are known in the prior art, and are illustrated in several prior art patents. These include, for example, U.S. Pat. Nos. 4,937,895, 4,748,699, 5,073,995, 5,086,524, 5,040,247, 4,945,578, and 4,651,359.
The principle underlying all of these prior art devices is that as the toilet tank fills, the devices float upwardly around the overflow pipe, so that they are clear of the flapper valve at the bottom of the toilet tank, which covers the outlet to the toilet bowl. When the toilet is flushed, by virtue of the flapper valve being raised to uncover the outlet, the water level in the tank drops and the device drops down with it, at a certain point coming into contact with the flapper valve to push it back to the closed position prematurely, i.e. before all of the water has drained from the tank. This results in a substantial saving of water, and yet in most cases an effective flush is still achieved. The full pressure head of water in the tank is used, which would not be the case if the water saving was effected by virtue of the tank being only partially filled, for example.
Several of the prior art devices involve upper and lower halves which are moveable towards and away from each other to vary the point at which the flapper valve will be contacted to close it. See for example U.S. Pat. No. 4,748,699. In such an arrangement, however, there is some potential for the device to hang up on the float arm in some toilet tank configurations, by virtue of the float arm becoming caught on the underside of the upper cup shape.
In other devices, such as in U.S. Pat. No. 4,945,578, there is no positive means of locking the two cup shapes together in any given position, so that there is potential for the relative position of the cups to change with time. Some devices have recognized this problem, and thus in U.S. Pat. No. 4,937,895, a threaded design is used.
A problem in some toilet tanks is that the overflow pipe may be positioned quite close to the rear wall of the tank, or the tank may be insulated. In either event, there may be very little space between the overflow tube and the rear wall or insulation of the tank. This potential problem has been recognized by providing a cup which has a flattened side, as in U.S. Pat. No. 4,937,895.